'merge' and 'matched' keywords in sql
More SQL fixes:

- 'database' keyword
- don't start operators in the middle of the word
Added 'hljs-' prefix to '.phony'
Drop high relevance for Python class definitions.
They aren't defined strictly enough and can be recognized in the middle
of the sring in other languages. Functions starting with 'def' don't
have this problem though.
Improvements for Objective C:

- @-keywords defined with the actual '@' symbol to not mess
  with other languages
- custom `begin` for classes instead of beginsWithKeyword
- 'id' renamed to 'title' for default styling